Chad rebels due to take part in landmark talks with opposition groups and the military government on Saturday threatened to pull out citing "provocations and attempted aggression" by the government.
Preparatory negotiations in Qatar ahead of a mooted inclusive full national dialogue has been stalled for months with landlocked Chad mired in turmoil after long-time leader Idriss Deby Itno died fighting rebels last April.
His son Mahamat Idriss Deby Itno seized control but promised free elections this year ahead of which he had wanted a national dialogue to start on May 10.
Before that dialogue, the government and more than 40 opposition groups sent delegations to the Qatari capital Doha for preliminary talks.
But these remain stalled having initially been slated for February 27, then put back at the last minute to March 13.
In Saturday's joint statement, the armed groups accused the government delegation of acting in concert with "agents provocateurs" in order to "stall negotiations through harassment and intimidation, provocations and attempted aggression with a view to creating physical incidents".
The rebel groups said that while they "restated their desire to reach a peace accord ... they "reserve the right to suspend their participation or withdraw from the talks".
They added that were that to come to pass, "the government will bear the entire responsibility".
The government responded with frustration.
"Why would we sabotage a dialogue which we ourselves wanted," spokesman Abderaman Koulamallah told AFP, insisting that "negotiations are advancing well, each party has to take a step towards the other."
Qatar has previously helped in peace efforts for Yemen, Lebanon, Sudan and between the Afghan Taliban and the US government.